Forest fires are the cause of the ruination of our woodlands, destroying not only landscapes and ecosystems, which take a long time to recover, but also ruining the wealth of different kinds of wood, the forestry industry, destroying or damaging crops and buildings, and provoking casualties that affect both people and animals.
In order to respond to these fires a multiplicity of efforts have been made, not solely to prevent them but fundamentally to put them out once they have started. Thus, at the present time, the rapid extinguishing of such fires has become a priority.
These days, along with the participation in the work of extinguishing fires by squads of firemen and other persons who fight the fire on the ground, extensive advantage is also taken of the use of planes and helicopters that, because of their unrestricted movement can reach parts of the fire that would otherwise be inaccessible, or wooded areas that the ground squads would take time to reach, or perhaps would not be able to reach. In short, planes and helicopters benefit from the speed with which they can cover distances and also from their capacity to carry and deliver large quantities of water to determined points. In this sense, helicopters are preferred to planes or hydroplanes, due to the fact that they can refill with water from a wider range of locations.
The usual procedure for refilling a helicopter with water is to hang a bucket from it, suspended from the helicopter's cargo hook, then submerge the bucket in a lake, for example, and when it is full to takeoff with the load of water hanging below.
Subsequently, in order to drop the water from this bucket onto the chosen area, the pilot will take up a position above that area and open the bucket release valve, allowing the water to fall, by gravity, onto the fire. The inconvenience of this method is that all of the water is released in one drop, with the result that it is not very effective. In many cases this means that the helicopter will have to return to a determined area various times to make successive drops, in order to correct deviations during the water drop, caused by wind, turbulence, etc.
Moreover, following a first drop, residual areas frequently remain that were not reached by the water, or residual focuses of fire that need to be attacked again. To do so it is necessary, using the previously known technique, for the aircraft to pass over the same area various times, which represents an excessive waste of time.
Moreover, it must also be taken into account that, on occasions and due to the high temperatures produced by these fires, the water may even be vaporised before it can reach the ground, rendering it ineffective for purposes of extinguishment.
For the above reason, it has been found to be much more effective for the water to be combined with flame retardant or inhibiting substances. On the one hand this avoids vaporisation of the water while, on the other, it allows for fire inhibiting films to be applied to flammable objects that need to be protected, such as trees or buildings.
In addition, the formation of an extinguishing mixture, using the same quantity of water, will ensure that far more product is obtained, to be dropped on the fire, and, as mentioned above, a far more effective product.
To this end, provision must be made for the mixing of the fire-fighting composite while, at the same time, while simultaneously maintaining the capacity, in a device such as the present invention, for refilling with water.
Spanish patent no. 0419040, to Alexander Linkewich, disclosed the production of a fire-fighting paste, produced by adding water to fire-retardant products, such as ammonium sulphate mixed with clay and a binding agent. Given that the loading of this paste has to be done on the ground, the patent proposes filling the tanks of the aircraft with this fire-retardant product, subsequently filling the bucket with water, and mixing the two together en route.
The drawback of this system is that it is very difficult to maintain the mixture in optimum conditions for use. To this end a complex ground and aerial infrastructure is required, given that the mixture is in need of constant stirring/agitation.
U.S. Pat. No. 4,240,507, to Hokkanen, discloses a cistern, for aerial use. This bucket has one or more openings at the bottom to allow for filling, which are closed by means of a gate. The additive to be mixed with the water is then contained in another cistern. The apparatus includes a mechanism that controls the mixing of the additive with the water by means of two valves, dependent on the stroke of a piston, in such a way that it will, in one case, mix water with an additive and, in another, will release the mixture onto the fire. Finally, it will also return any excess and unused additive to its storage cistern.
U.S. Pat. No. 4,601,345, to Mahrt, discloses a device to mix and supply an extinguishing mixture, made up of water and a fire retardant agent in a tank or cistern. Equipped with a tank, containing the fire-retardant substance, located within the structure of the apparatus itself, plus another cistern containing water, suspended in the air. Using an injection pump the retardant substance is then transferred from one tank to the other to be mixed with the water, which is filled using conventional methods. The rotation of a propeller fixed to the end of the injection lance serves as a stirrer/agitator, which serves to speed up the mixing process.
PCT Patent No. WO94/28975, to As LuftTransport, discloses a tank to be used for an extinguishing mixture, to which is fitted the means to avoid the rotation of the module and to allow the pilot to control operation by means of radio communications. It is also fitted with a device that, along with a device that, by means of a cone that can be moved at the pilot's discretion, controls the strength of the mixture, allowing for discrete dosage of the quantity of the mixture poured in. Dosage is gravity based and the retardant substance is added directly to the bottom of the tank, or bucket, so that the mixing with the water is carried out on the basis of mutual contact.
Unfortunately, all of the above mentioned patents fail to provide an efficient and effective way of producing fire-fighting foam, insofar as the production of such foam requires that it be mixed with air. Mixing fire-retardant paste directly with water requires quite a lot of time for the additive to become adequately blended in, while agitating or stirring the water is an ineffective solution, as alternatively is expecting that, during the drop of the mixture onto the fire, sufficient time will have passed for the foam to fully form, due to the mixture coming into contact with the air.
The negative consequence of this are that the extinguishing mix dropped onto the fire is deficient and, moreover, considerable time needs to be spent making up the proposed mixture.
Furthermore, as discharging times are very short, extinguishing is limited to the area of impact.
PCT Patent No. WO9423797, to Baker R., discloses a tank that supplies foam for the extinguishing of fires by using bottled compressed air, the pressure of which allows for the spraying of the foam mixture through a series of nozzles controlled by valves, which spray the foam onto hemispherical aeration screens in order to fully expand it.
However, as this tank requires the use of compressed air maintenance requirements are complicated. Moreover, it also depends on an external source of maintenance, which requires ground assistance for it to be operative. It also lacks the means to ensure the controlled mixing of the foam and water, this being done passively in the hold of the tank which is filled on the ground. As there is no automatic and successive loading of the water, the extinguishing performance of the tank decreases notably. In addition, the dropping of the foam is practically gravity driven, insofar as a sufficient impulse is not generated to activate the foaming.
Thus we can see that, in the systems that are known to date, the dropping of the water is only by means of gravity, and despite the fact that foaming elements are mixed in and aeration of the foaming agent does occur during the drop, these systems are not very effective.
Furthermore, the foam produced is neither homogeneous nor fully expanded, which results in important water losses and an inability to take full advantage of all of the advantages that such foam can provide as an extinguishing element.
The device of the present invention, conversely, is not gravity driven but is driven by the pressure of an expulsion pump that sprays out the fire-extinguishing substance, and this means that it can be used with discretion and in successive applications, in this way rectifying the disadvantages mentioned above.
The foam is discharged at a determined pressure, completely expanded and homogeneous, with the result that an extinguishing product is obtained that is more effective and that provides a higher level of mixture performance.
A further and additional advantage is that the new device uses much less water than conventional devices do, decreasing the load that needs to be carried by the aircraft, improving handling, and allowing the aircraft to fly at reduced speeds, or even at hover, ensuring much more precise and effective fire-extinguishing.